Cognitive dysfunction is clearly recognized in bipolar patients, but the degree of impairment varies due to methodological factors as well as heterogeneity in patient populations. Researchers set out to evaluate cognitive functioning in bipolar patients and to assess its association with depressive symptoms. In addition, the relationship between cognitive functioning abilities and lifetime alcohol use disorder was further explored. Check the end of this report to download this open access article.
Methodology
The study included 110 bipolar patients and 75 healthy controls (ages 18 to 65 years). Patients with severe depressive symptoms, (hypo)manic symptoms and current severe alcohol use disorder were excluded. Diagnoses were evaluated via the Mini-International Neuropsychiatric Interview. Cognitive functioning was measured in domains of psychomotor speed, speed of information processing, attentional switching, verbal memory, visual memory, executive functioning and an overall mean score. Severity of depression was assessed by the Inventory of Depressive Symptomatology – self rating.
Principal Findings
Patients were euthymic (n = 46) or with current mild (n = 38) or moderate (n = 26) depressive symptoms. Cognitive impairment was found in 26% (z-score 2 or more above reference control group for at least one domain) of patients with the most prominent difficulties found in executive functioning (effect size [ES] = 0.49) and speed of information processing (ES = 0.47).
”Total
Depressive symptoms were associated with dysfunction in psychomotor speed (r-squared [R2] = 7%), speed of information processing (R2 = 20%), attentional switching (R2 = 16%) and the mean score (R2 = 24%), but not with verbal and visual memory and executive functioning.
Depressive symptoms explained 24% of the variance in the mean z-score of all 6 cognitive domains.
Comorbid lifetime alcohol use (n = 21) was not associated with cognitive dysfunction.
Conclusions/Significance
Cognitive dysfunction in bipolar disorder is more severe in patients with depressive symptoms, especially regarding speed and attention. Therefore, interpretation of cognitive functioning in patients with depressive symptoms should be cautious. No association was found between cognitive functioning and lifetime comorbid alcohol use disorder.
Material adapted from PLoS ONE.
Download / Reference
van der Werf-Eldering MJ, Burger H, Holthausen EAE, Aleman A, & Nolen WA (2010). Cognitive Functioning in Patients with Bipolar Disorder: Association with Depressive Symptoms and Alcohol Use. PLoS ONE 5(9): e13032. doi:10.1371/journal.pone.0013032
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